Accurate landing elevator systems



3 Sheets-Sheet 1 RED SWI

May 14, 1957 Filed Aug. 51, 19?;

INVENTOR James Dunlop av ATTORNEY May 14, 1957 J. DUNLOP ACCURATELANDING ELEVATOR SYSTEMS 3 Sheets-Sheet 2 Filed Aug. 51, 1954 Fig.2A.

mm NW HWK m m w. W W ww W 5W w 35 E A E A E n May 14, 1957 Filed Aug.31, 1954 J. DUNLOP ACCURATE LANDING ELEVATOR SYSTEMS 3 Sheets-Sheet 3United States Patent '0 ACCURATE LANDING ELEVATOR SYSTEMS James Duulop,Ridgewood, N. J., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application August 31,1954, Serial No. 453,370

13 Claims. (Cl. 18729) The invention relates to motor control systemsand, more particularly, to a system for controlling the retardation ofan elevator car prior to stopping.

In elevator systems, particularly those employing a single-speedalternating-current hoisting motor, slowdown or retardation andautomatic stopping of the car level with a station, such as a floor,presents a problem, because stopping is usually initiated at a fixedpoint in the hatchway with respect to the floor, and varying loadingconditions of the car result in varying car speeds during the stoppingoperation. Accordingly, a system adjusted for a certain car load mayresult in over-shooting or stopping short of floor level with difierentcar loads or different directions of car travel. This problem isdiscussed, for example, in Patents 2,491,948 and 2,676,673.

In accordance with the invention, an elevator system is provided with abrake for stopping the elevator car at predetermined stations or floors.Slowdown is initiated when the elevator car is a predetermined distancefrom a station at which it is to stop by applying a brake to produce abraking effort dependent on the load carried by the elevator car. Whenthe elevator car is adjacent the station at which it is to stop, thesame brake may be applied to produce a predetermined braking efiortindependent of the load in the elevator car.

It is an object of the invention, therefore, to provide an improvedcontrol system for elevators in which the elevator car may be slowed andstopped accurately at a predetermined station, regardless of the load onthe car.

It is a further object of the invention to provide a.

control system for a single-speed alternating-current mo tor employing abrake having plural operating mechanisms in which the motor may beaccurately stopped regardless of variations in loading conditions on themotor.

Another object of the invention is to provide an improved braking systemhaving plural operating mechanisms acting on a common brake.

Other objects will be apparent from the following description andaccompanying drawings, in which:

Figure 1 is a schematic illustration of an elevator system embodying thepresent invention which may be used;

Fig. 2 is a schematic diagram of a control circuit for the systemillustrated in Fig. 1;

Fig. 2A is a key-diagram which indicates the positions of the variousrelays and their contacts as shown in Fig. 2;

Fig. 3 is a schematic view of an inductor relay used in connection withthe invention; and

Fig. 4 is a view in elevation with parts broken away of abrake assemblysuitable for the system of Fig. 1.

Referring more particularly to Fig. 1, the elevator system includes anelevator driving motor 2 which may be of the single-speedalternating-current squirrel-cage type, and which may comprise anarmature 3 and a three- Patented May 14, 1957 phase Y-connected statorhaving windings a, b, and c.

The shaft of armature 3 extends into a reduction gearing 4, which may beof a worm-gear type, the output of which drives a hoisting sheave 6,about which the hoisting rope or cable 8 extends, connecting a suitablecounterweight 9 with the elevator car 10.

A service brake 12 includes a brake drum 14 mounted on the motor shaftand has associated with it a brake shoe 11, which is spring-pressed intobraking engagementwith the drum by a spring 15. A brake winding v C, tobe energized when the elevator is in operation,

is effective to release the brake against the force of spring 15.Normally, winding C will be deenergized during the stopping operation topermit the application of the brake shoe 11, which will stop the car andhold it in its stopped position.

The brake shoe 11 also may be urged against the brake drum in responseto energization of a winding B, even though the winding C is energizedto release the brake. A suitable construction for the brake will bediscussed in greater detail below.

A tachometer generator T6 is also mounted on the motor shaft to bedriven in accordance with the motor speed, and includes separatelyexcited field winding TGF.

In order to control circuits in accordance with the position of theelevator car in its hoistway, suitable control contacts are provided.For present purposes, the control contacts are assumed to be provided byinductor relays.

An inductor relay 26 is mounted on the car 10 for movement therewithpast a plurality of plates 22 and 23, of magnetic material, mounted inthe hatchway at fixed points with respect to the various floors to beserved. This type of relay is indicated more clearly in Fig. 3, and isof a well-known type as shown, for example, in Santini Patent 2,298,174.Briefly, the relay includes a winding I and normally-closed contacts DLand UL. The magnetic circuit of the relay is such that even though thewinding I is energized, the contacts UL and DL will remain closed untilthe relay registers with a plate 22 or 23, at which point the magneticcircuit is completed by such plates to open the respective contacts DLor UL. For example, as shown in Fig. 3, the position of the relayindicates that the car is stopped accurately at floor level, at whichpoint both plates 22 and 231 are efiective to open the contacts UL andDL, respectively.

However, upon movement of the relay with respect to the plates,sufiicient to clear the relay from the magnetic influence of the plates,the contacts DL and UL will close. In other words, if the car'and itsrelay' move 1 upward, as indicated by the arrow in Fig. 3, a relativelysmall movement will cause the contacts DL to close, and the converse istrue for contacts UL for downward car movement.

A slowdown inductor relay 265 also is provided having two normally-opencontacts ISU and 15!). If they winding of the relay is energized, thecontacts remain open until the relay reaches a magnetic plate 228 or233. Thus, if the elevator car when traveling up reaches a point atwhich it should slow down to stop at a floor, the inductor relay reachesthe magnetic plate 238 for such floor to complete a magnetic circuit,which results in closure of the contacts ISU. When once closed, thecontacts remain closed until the winding of the relay is deenergized,even though the relay leaves the magnetic plate. Similarly, during downtravel, if the elevator car reaches a point at which it should slow downto stop at a floor, the magnetic plate 228 for such floor completes amagnetic circuit, which results in closure of the contacts I SD. Thesecontacts remain closed until the p the art.

The windings a, b, and c of the hoisting motor 2 are energized from athree-phase alternating-current supply including leads L1, L2, and L3.The energization of the motor is primarily controlled by the contactsM3, and the direction of rotation of the motor armature is controlled bythe contacts U2 and D2 which are efiective to reverse the connections tothe motor windings a and b.

An iron core reactor 30 is connected in series with the lead L2 and isshunted by a circuit including normallyopen contacts V1 by a circuitincluding normally-closed contacts E1 and normally-open contacts F1, orby a circuit including a manually-operated switch SW1. The reactor 30 isof the saturable type, including a control winding A which is energizedas hereinafter described.

Suitable mechanism is provided which is responsive to the load in theelevator car. To illustrate such mechanism, a load weighing platform Pis provided which is deflected in accordance with the load thereon. Theplatform operates taps which control the effective resistance value oftwo resistors REU and RED. If the switch SW is in the positionillustrated, the winding B is connected to be energized from the directcurrent buses I(+) and II() through make contacts E2 and either of twopaths. One path is effective for up travel of. the elevator car andincludes the make contacts U5 and the resistor REU. The second path iseffective during down travel and includes the make contacts D5 and theresistor RED.

The starting and stopping of the elevator car conveniently may becontrolled by the circuit shown in Fig. 2. Referring particularly tothe'lower portion of the diagram, the alternating-current leads L1 andL2 constitute the input to a full-wave rectifier 36, which may be abridge of copper-oxide rectifiers, and the output of the rectifier isconnected to provide positive lead 1+ and a negative lead II-, acrosswhich the control relay windings are connected.

' There are many conventional types of elevator starting'and stoppingcircuits which may be employed, but as a relatively simple example, itwill be assumed that the car will be started and its stopping initiatedby a car switch CS mounted in the elevator car. Up direction switch Uand down direction switch D are provided to control the direction ofrotation of the elevator motor 2, depending upon the direction ofmovement of the car switch handle. Slowdown of the elevator car afterthe car switch handle has been centered will be controlled by theinductor relay 265 as it reaches a plate 228 during down travel or aplate 233 during up travel, and the stopping of the car after the carswitch handle has been centered will be controlled by the inductor relay26' as it reaches a plate 22 or a plate 23, depending upon the directionof car movement, to open respectively its con-' tacts UL or DL.

- As an assumed operation, with the elevator car standing at a floor andwith its door open, if the operator desires to travel to a higher floor,he will first close the door. This will complete the circuit through thedoor interlocks and the winding of relay DR, assuming all the other doorcontacts of the installation are closed. t will be understood that inaccordance with conventional practice, each hoistway door and the cardoor (not shown) has interlock contacts which are closed only when theassociated door is closed. The interlock contacts in series control therelay DR. Winding of relay DR will then close its contacts DR effectinga connection between the postive leadl+ to the movable contact of thecar switch CS. When the operator moves the car switch handle in acounterclockwise direction, for upward car movement, contact 38 will beengaged completing a circuit through the up direction switch U, closedcontact D1, and the car running relay M. Contact 39 is disengaged andthe relay' F drops out to open itscontacts F1.

Relay U will open its contact U; in the circuit of the down directionswitch D to prevent energization thereof, and will close its contacts U2in the motor leads L1 and L2, which will permit appropriate rotation ofthe motor for the up direction.

Relay M will close its contacts M3 in the leads L1, L2, and L3 tocomplete the circuit for the motor and, at the same time, will closecontacts M2 to energize the winding C of service brake 12, to releasethe brake, contacts U3 being already closed. The car will now move inthe up direction, but at a relatively low speed because of the reactor30 in lead L2 of the motor which interposes a relatively high impedanceand results in a reduction of motor torque to a low value.

Further movement of the car switch handle in the counterclockwisedirection will bring the car up to normal speed. Contact 40 is engagedby the car switch to energize relay V, contacts DRZ having already beenclosed upon energization of relay DR when the door interlock circuit wascompleted.

Relay V will close its contacts V1 in the shunt circuit around thereactor 30 which restores complete energization of the motor lead L2 andbrings the motor up approximately to synchronous speed. it Will opencontacts V3 to deenergize the coils I and IS of the inductor relays.Contacts V4 will also be opened for a purpose to be described. ContactsV2 open to deenergize the relay E.

Assuming that the car is now traveling up at full speed, and a stop isintended, the operator centers the can switch CS, thereby breaking thecircuit to contacts 38 and 40, and energizing contact 39 to pick up therelay P which has contacts F1 completing with contacts E1 a shunt acrossthe reactor 30. Opening the circuit at 40 deenergizes high-speed relayV, which results in (1) opening V1, (2) closing V2, (3) closing V3 toenergize inductor windings I and IS, and (4) closing V4 to complete aholding circuit for direction switch U and running relay M throughclosed inductor contacts UL.

Disregarding for the moment the control of brake coil B and the biascoil A of the reactor 30, the car will proceed until a plate 228adjacent the desired landing becomes efl ective to close the contactsISU. This results in energization of the relay E through the contactsISU and V2, and the relay E opens its contacts E1 to render the reactor30 effective for reducing the motor torque. Closure of contacts E4completes with contacts V2 and M4 a holding circuit for the relay E.(The energization of the coil B due to closure of contacts E3 and theeffect thereof on slowdown of the elevator car will be discussed below.)

As the car continues, a plate 22 adjacent to the desired landing becomesefiective to open the contacts UL. Contacts UL when open will deenergizethe up direction switch U, which will open the contacts U3 in thecircuit of coil C of the service brake 12 and permit application of the,

brake under the influence of its operating spring 15 to stop the car andhold it in stopped position. Contacts U2 in the motor winding leads willreopen and relay M being deenergized along with switch U, contacts M3 inthe motor leads will open, completely disconnecting the motor from thesource of supply.

It is contemplated that during slowdown, the brake 12 will be applied toassist in the slowdown operation by absorbing the stored energy in thesystem. This actuation of brake 12 is effected by coil B in a circuitshown in the 7 upper portion of Fig. 2. The circuit 44 includes seriesconnected iron-core reactors 46 and 48, a full-wave rectifier bridge 50,and the contacts E3 which closed when relay E picked up. The output ofthe bridge 5'0 includes windings 52 and 54, connected in opposition, forthe reactors. 48 and 46, respectively, and the brake coil B. The switchSW is assumed to be in its upper position.

The impedance of reactors 46 and 48, is normally such that brake coil Bwould not be efiectively energized, but

such impedance may be reduced by the biasing coils 60 and 62 for thesereactors, which coils are also connected in opposition. The energizationof biasing coils 60 and 62 is controlled in the following manner.

At the point of initiating slowdown (when car switch CS is centered andthe slowdown inductor relay operates) the tachometer generator TG isoperating at substantially full speed, with its field TGF connectedacross the direct current leads 1+ and 11-. Assuming that at this time,with the car traveling up, the right-hand output terminal of TG ispositive, contacts U4 being closed, the full output of TG is impressedon the biasing coils 6t) and 62 through a circuit including a one-wayrectifier 66, thereby decreasing the impedance of reactors 46 and 48 toa minimum, and permitting maximum energization of the brake coil B. Therectifiers 66 and 68 permit flow of current therethrough in thedirections of the arrows adjacent thereto, respectively.

Coil B then operates to apply brake shoe 11 to its drum to slow theelevator, in addition to the motor-torquereducing effect of reactor 39in lead L2, to further overcome the inertia of the system. As theelevator speed decreases, the output of TG also decreases until itsvoltage is balanced against an opposing voltage, or pattern voltage,from the voltage divider, the tap R being preferably so set that suchbalance occurs at 10% full speed of the elevator, but, of course, otherspeeds may be chosen as desired, depending upon theoperation required.When the two voltages are equal, no current will flow in the biasingcoils 60 and 62, thereby rendering the impedance of reactors 46 and 48of maximum value, and hence providing a minimum energization of brakecoil B. Accordingly, the brake initially has a maximum retarding effectwhich decreases as the elevator speed decreases to a minimum retardingaction at the 10% speed point.

During the slowdown of the car to the 10% optimum, biasing coil A ofreactor 30 has been substantially deenergized because the positiveoutput of TG has been blocked by a rectifier or valve 63. Accordingly,coil A has had no effect on the high impedance of reactor 30,maintaining a low-torque energization of the motor 2.

If the elevator speed tends to fall below the 10% optimum because ofload on the car, the output of TG further decreases to a point where thevoltage divider component will predominate, whereupon the direction ofcurrent flow through the armature of TG reverses. This will not affectthe biasing coils 60 and 62 because of the rectifier 66, but it willenergize the winding A of reactor 30 in accordance with the output ofTG, which will have the efiect of reducing the impedance of reactor 30,causing an increase in motor torque to tend to bring the motor speedback to the 10% value. The motor will then arrive at a speed where thetorque equals the load on the car, or at least be sufiicient to maintainthe desired landing speed without regard to the load on the car.

At a higher load, the speed of the car and, hence, the output of TGwould further decrease, thereby increasing the energization of bias coilA, which further decreases the impedance of reactor 30, which, in turn,provides an increased motor torque to take care of the higher load.

'With the apparatus and system disclosed, an automatic landing systemfor an elevator has been provided which is substantially independent ofvariations in loading conditions on the car over a rather wide range. Byreason of the reactor 30 and its biasing winding, effective slowdownspeed is readily obtained, and the stopping action is facilitated by thebrake which provides a smooth braking torque applied at a maximum forceupon initiation of slowdown and gradually decreases as the car slows toa desired speed, the rate of decrease depending upon the speed of thecar which, of course, is a function of the load on the car.

In order to move the elevator car in the down direction, the car switchCS is rotated in a clockwise directionto energize the relays V and D.The efiect of energization of the relay V previously has beenconsidered. The energization of the switch D in place of the switch Uconditions the elevator system for operation in the down direction.Thus, the switch D opens its break contacts D1 to prevent energizationof the up switch U. Contacts D2 close to connect the motor 2 forenergization in the proper direction for down travel. Contacts D3 closeto complete with the contacts M2 an energizing circuit for the Winding Cof the brake.

inasmuch as reversal of the direction of movement of the elevator carreverses the direction of rotation of the tachometer generator TG, thecontacts U4 and D4 operate as reversing switches for the tachometergenerator. Closure of contacts D4 connects the tachometer generator withproper polarity for down travel of the elevator car.

It the elevator car is to stop at a floor, the switch CS is centered todeenergize the relay V and energize the relay F. These relays previouslyhave been discussed. When the inductor relay IS reaches the inductorplate 22S associated with the floor at which the elevator car is tostop, the contacts ISD close to energize the relay E. Such energizationinitiates a slowdown of the elevator car by the sequence previouslydiscussed.

As the elevator car nears the floor at which it is to stop, the inductorrelay 26 open its contacts DL to deenergize the down switch D and therelay M. As a result, the contacts D2 and M3 open to deenergize themotor 2, and the contacts D3 open to deenergize the winding C of thebrake. Consequently, the elevator car stops accurately at the desiredfloor.

The invention also may be incorporated in a system wherein no provisionis made for decreasing the torque exerted by the motor 2, and whereinthe tachometer generator TG is not employed. To illustrate such asystem, it will be assumed that the switch SW occupies the positionillustrated in Fig. 1, and that the switch SW1 is closed to shunt thereactor 30.

The elevator car is started in the manner previously described. However,since the switch SW1 is closed, the full torque of the motor 2 isemployed for starting the elevator car.

Let it be assumed that the elevator car is traveling up and that it isapproaching a floor at which it is to stop. Under such circumstances,the elevator car attendant centers the car switch CS to deenergize therelay V and energize the relay F. Under the assumed conditions, therelay F has no eilect on the operation of the system. The relay V,however, closes its break contacts V3 to energize the windings of theinductor relays. Closure of break contacts V2 and V4 has no effect onthe immediate operation of the system. As the elevator car continues itsapproach to the desired floor, the inductor relay 26S reaches the plate235 associated with such floor, and the contacts ISU close to energizethe relay E. This relay closes its make contacts E4 to establish withthe closed break contacts V2 a self-holding circuit. In addition, makecontacts E2 (Fig. 1) close to complete with the closed make contacts U5of the up switch U an energizing circuit for the Winding B. Themagnitude of the energization of the winding B is determined by theeffective resistance value of resistor REU, and this, in turn, isdetermined by the loading of the elevator car.

- Thus, for a full load the maximum value of the resistor REU isavailable and the winding 13 has its minimum energization. Under thesecircumstances, the brake has little retarding effect on the elevatorcar. For a light load in the elevator car a minimum eifective value ofresistance is provided by the resistor REU, and the winding B isenergized substantially to provide a substantial braking effort.Consequently, the braking effort is automatically adjusted to retard theelevator car substantially to a predetermined landing speed within apredetermined distance for all loadings of the elevator car. Theelevator car 7 drivingmotor may be deenergized during this slowdownoperation, but for present purposes, it will be assumed that the drivingmotor is energized.

When theelevato-r car is adjacent the floor at which it is to stop, thecontacts UL of the inductor relay 26 open to deener'gize the up switch Uand the relay M.

Opening of the contacts U2 and M3 deenergizes the driving motor 2.Opening of the contacts U3 and M2 deenergizes the. winding C, and thespring 15 applies the brake 12 to stop the elevator car accurately atthe desired floor.

If the elevator car is traveling in the down direction, slowdown of theelevator car to a landing speed is efiected in a somewhat similarmanner. Under these circumstances, when the inductor relay 26S reachesthe plate 228 associated with a floor at which the elevator car is tostop, contacts 18D close to energize the relay E and close the makecontacts E2. Since the make contacts D5 are closed under theseconditions, the winding B is now energized through the resistor RED.This resistor has an effective value, depending upon the loading of theelevator car. For a full load, the resistor has its minimum value, andthe winding B has its maximum energization to provide a substantialbraking efiort. If the elevator car is lightly loaded, the resistor REDhas a substantial eiiectiv'e value, and the winding B provides a smallerbraking effort. Thus, for both up and down travel of the elevator car,the winding B assures slowdown of the elevator car to a desired landingspeed in a predetermined distance, regardless of the loading of theelevator car. a

The brake also is applied by the winding B during a leveling operationinitiated by the contacts UL or DL. Consequently, the elevator car ismoved to its level position against a braking effort determined by thevalue of the car loading.

A suitable construction for the brake 12 i illustrated in Fig. 4. Itwill be noted that two brake shoes 11 and 11A are provided. Since thesebrake shoes are operated in a similar manner, it will sutfice todescribe in detail the operating mechanism for the brake shoe 11,Components of the operating mechanism associated with the brake shoe 11Awill be identified by the same reference characters employed for thecorresponding components associated with the brake shoe 11 to which thesuflix A has been added for the purpose of identification.

The brake drum 14 is mounted for rotation relative to a supportingstructure 7t). A brake arm 71 has one end pivotally mounted on thesupporting structure 79 and has its remaining end biased in acounterclockwise direction, as viewed in Fig. 4, by means of a spring 15which is compressed between the brake arm 71 and a washer '72. TheWasher 72 is secured to the supporting structure 70 by means of a stud73.

Inasmuch as the brake shoe 11 is secured to the arm 71, movement of thearm about its pivot actuates the brake shoe into braking engagement withthe drum 3.4 or away from the drum. it will be noted that the spring 15urges the brake shoe 11 into braking engagement with the drum 14.Release of the brake shoe from the drum is effected by energization ofthe winding C. Such energizc tion results in downward movement of amagnetic armature or plunger 74. The plunger engages one arm of the bellcrank '75. The other arm of the bell crank engages a screw 76 which isin threaded engagement with the arm 71. Consequently, when the winding Cis energized, the arm 71 is forced against the bias of the spring 15 tocarry the brake shoe 11 away from the drum 14.

The brake shoe 11 is so mounted that it may be up enated independentlyor". the arm '71 for a limited distance into and out of brakingengagement relative to the drum 14. To this end, a tubular slider 77 ismounted for reciprocation in the arm 71. The left-hand end of theslider,-as viewed in Fig. 4, engages a projection 78 extending away fromthe brake shoe ll. Although the brake shoe may be rigidly secured to theslider 77, preferably the engagement between the two permits thealignment of the brake shoe relative to the drum. To this end, theengaging surfaces or" the projection 73 and the slider 77 have anarcuate configuration. Although a spherical configuration may beemployed to obtain a universal alignment, a configuration which iscylindrical about an axis parallel to the axis of the drum issuflicient. The projection 78 is urged against the slider 77 by means ofa spring 79, which is located within the slider and which is compressedagainst the left-hand end of the slider by means of a link 80 which hasone end pivotally secured to the projection 78. The remaining end of thelink is provided with a head. By inspection of Fig. 4, it will be notedthat the spring 78 is compressed for the purpose of urging theprojection 78 against the adjacent end of the slider 77.

The brake arm 71 has a wall 81 provided with an opening for snugly andslidably receiving the slider 77. The slider at its right-hand end, asviewed in Fig. 4, is provided with a flange 82 for the purpose ofcompressing between the flange and the wall 81 a helical spring 83. Thisspring biases the slider into engagement with a plate 84, which issecured to the brake arm 71.

Movement of the slider against the resistance of the spring 83 iseffected through a plug 85, which is in threaded engagement with theslider 77. The plug 85 has a head projecting through an opening in theplate 84.

By inspection of Fig. 4, it will be noted that a lever 86 is pivotallymounted on the plate 84. This lever has a first arm 37 projecting intoengagement with the head of the plug 85. The lever has a second arm 88extending adjacent the winding B, which is mounted on the brake arm. Thewinding B is employed for actuating a magnetic armature or plunger 89.When the winding B is energized, the plunger S9 is actuated to theright, as viewed in Fig. 4, against the arm 88 of the lever 86 with aforce dependent on the magnitude of the energization of the winding.This force is transmitted through the lever to the slider 77 for thepurpose of moving the brake shoe 11 relative to the brake arm 71 intoengagement with the brake drum to produce a braking effort, depending onthe magnitude of the energization of the winding B.

It will be noted that regardless of the condition of energization of thewinding B, the force exerted by the spring 15 is available at all timesfor actuating the brake shoe 11 into braking engagement with the drum14. Consequently, the brake illustrated in Fig. 4 complies fully withall safety requirements for all elevator systems.

It will be understood that the winding BA may be connected in series orparallel with the winding B for the purpose of operating its associatedbrake shoe 11A in a similar manner. The plunger 74 associated with thewinding C operates through the bell crank 75A to release the brake shoe11A from the drum 14.

Although the invention has been described with reference to certainspecific embodiments thereof, numerous modifications falling within thespirit and scope of the invention are possible. Thus, although theinvention has been described as incorporated in a simple oar switchstart and inductor relay stop elevator system, the invention also may beapplied to automatic push button elevator systems for both passenger andfreight operation in which accurate stops at predetermined stations aredesired.

I claim as my invention:

1. In an elevator system, a structure for receiving an elevator car,said structure having stations to be served by an elevator car, anelevator car, motive means for reciprocating the elevator car relativeto the structure, a brake for stopping said elevator car at a station ofsaid structure, and brake-operating means comprising releasing means formaintaining the brake in released position, and applying meansresponsive to arrival of the elevator car at a predetermined distancefrom a station at which the elevator car'is to stop for initiating anoperation of the brake to stop the elevator car adjacent the desiredstation, said brake-applying means comprising means for renderingineffective the releasing mean-s, firstmechanism for applying the braketo restrain the elevator car, and second mechanism operablesubstantially independently of the first mechanism for applying thebrake while the releasing means is in releasing condition.

2. A system as claimed in claim 1 wherein the brakeoperating meansoperates the second mechanism to develop a brake retarding forcedependent on the loading of the elevator car to assist in slowing theelevator car substantially to a low landing speed within a predetermineddistance of travel of the elevator car following said initiation ofoperation of the brake.

3. A system as claimed in claim 1 wherein said first mechanism isefiective for applying substantially a predetermined force to the brakewithout substantially affecting the condition of the second mechanism.

4. In an elevator system, a structure for for receiving an elevator car,said structure having stations to be served by an elevator car, anelevator car, motive means for reciprocating the elevator car relativeto the structure at a rate of movement which varies as a function of theload on the elevator car, a brake for stopping said elevator car at astation of said structure, and brake-operating means responsive toarrival of the elevator car at a predetermined distance from a stationat which the elevator car is to stop for initiating an operation of thebrake to stop the elevator car adjacent the desired station, saidbrake-operating means comprising mechanism responsive to arrival of theelevator car within a predetermined distance of a station at which it isto stop for applying the brake with a force dependent on the loading ofthe elevator car to slow the elevator car, and mechanism responsive toarrival of the elevator car adjacent the station at which it is to stopfor applying the brake with a predetermined force substantiallyindependent of the condition of the first-named mechanism.

5. In an elevator system, a structure for receiving an elevator car,said structure having stations to be served by an elevator car, anelevator car, motive means for reciprocating the elevator car relativeto the structure, a brake for stopping said elevator car at a station ofsaid structure, and brake-operating means responsive to arrival of theelevator car at a predetermined distance from a station at which theelevator car is to stop for initiating an operation of the brake to stopthe elevator car adjacent the desired station, said brake-operatingmeans comprising mechanism for moving the brake from a released positionpermitting movement of the elevator car to an applied position forrestraining movement of the elevator car, and means dependent on theloading of the elevator car while approaching a station at which it isto stop for advancing the brake relative to said mechanism intobrake-applied position.

6. In an elevator system, a structure for receiving an elevator car,said structure having stations to be served by an elevator car, anelevator car, motive means for reciprocating the elevator car relativeto the structure, a brake for stopping said elevator car at a station ofsaid structure, and brake-operating means responsive to arrival of theelevator car at a predetermined distance from a station at which theelevator car is to stop for initiating an operation of the brake to stopthe elevator car adjacent the desired station, said brake-operatingmeans comprising mechanism for moving the brake from a released positionpermitting movement of the elevator car to an applied position forrestraining movement of the elevator car, and means dependent on theloading of the elevator car while approaching a station at which it isto stop for advancing the brake relative to said mechanism intobrake-applied position with a force dependent on the loading of theelevator car.

' 7. In a brake assembly, a supporting structure, a mem ber mounted formovement relative to the structure and requiring braking, a brake shoe,mounting means mounting the brake shoe for movement towards and from thebrake member, mechanism associating the brake shoe with the mountingmeans to permit limited movement of the brake shoe relative to themounting means towards and from the brake member, biasing means biasingsaid mounting means to urge the brake shoe towards the brake member,brake-releasing means operable for forcing the mounting means againstthe bias of the biasing means to release the brake shoe from the brakemember, and electroresponsive means operable for applying a force urgingthe brake shoe towards the brake member independently of the mountingmeans.

8. In a brake assembly, a brake drum, a brake shoe, mounting meansmounting the brake shoe for movement towards and from the brake drum,mechanism associating the brake shoe with the mounting means to permitlimited movement of the brake shoe relative to the mounting meanstowards and from the brake drum, biasing means biasing said mountingmeans to urge the brake shoe towards the brake drum, brake-releasingmeans operable for forcing the mounting means against the bias of thebiasing means to release the brake shoe from the brake drum, auxiliarymeans urging the brake shoe away from the brake drum with a force lessthan the force developed by the biasing means, and electroresponsivemeans acting between the mounting means and the brake shoe for urgingthe brake shoe against the resistance of the auxiliary means towards thebrake drum.

9. A brake assembly as claimed in claim 8 wherein the electroresponsivemeans is mounted on the mounting means.

10. In a brake assembly, a brake drum, a brake shoe, a brake support,means mounting the brake drum for rotation relative to the support, abrake arm pivotally mounted on the brake support for movement towardsand from the brake drum, lost-motion mounting means mounting the brakeshoe on the brake arm for movement with the brake arm into and out ofbraking engagement with the brake drum, the lost-motion of saidlost-motion mounting means permitting limited movement of the brake shoerelative to the brake arm towards and from the brake drum, biasing meansacting between said brake shoe and the brake arm to urge the brake shoeaway from the brake drum, and electromotive means mounted on the brakearm, said electromotive means being efiective when energized while thebrake shoe is spaced from the drum for actuating the brake shoe relativeto the brake arm into engagement with the brake drum.

11. A brake assembly as claimed in claim 10 in combination with biasingmeans acting between the brake arm and the brake support to bias thebrake shoe towards braking position, and electromotive means effectivewhen energized for operating the brake arm relative to the brake supportaway from braking position against the bias of the last-named biasingmeans.

12. In a brake assembly, a brake drum, a brake shoe, a brake support,means mounting the brake drum for rotation relative to the support,first motor means elfective when energized for controlling theengagement of the brake shoe with the brake drum, and second motor meansfor controlling the position of the first motor means and the brake shoeas a unit relative to the brake drum.

13. In a brake assembly, a brake drum, a brake shoe, a brake support,means mounting the brake drum for rotation relative to the support,first force-exerting means, linkage including a pair ofrelatively-movable components for coupling the force-exerting means tothe brake shoe, said relatively-movable components being eifective as aunit for transmitting force between the force-exerting means and thebrake shoe, and the movable components being relatively movable formodifying the position of the brake shoe relative to the brake drum,said force-exerting means being operable for moving the brake shoethrough the linkage into and out of braking engagement with the brakedrum, and motor means for controlling movement of one of said movablecomponents relative to the other of the movable components, said motormeans being efiective for moving said components relative to each otherto control the braking engagement of the brake shoe relative to thebrake drum.

References Cited in the file of this patent UNITED STATES PATENTS

